Is there a way to see full symbols in Titles and Comments using equations and expressions? Thanks.
These should be visible when viewing the site in a browser. If you mean using the mobile app, note that the mobile apps are no longer supported. However, you can tap on a comment and select an option to view the rendered mathjax. There is no such option for titles.
If it's not visible on the mobile site with the blue theme, you can select full site with a link at the bottom and you will get the responsive design, which is much like the full site on the desktop but with appropriate sizing for mobile devices.